Thermographic techniques to assess welfare during teeth grinding in piglets

Teeth resection of piglets within 24 hours of birth is a practice commonly applied in commercial farms to avoid facial injuries of littermates during establishment of teat orders and long term damage to the sow's udder. Opinion about resection and techniques is not unanimous among researchers and the debate is very heated. A preliminary study was implemented to ascertain whether novel thermographic techniques could be used to determine temperatures reached by the teeth and mouth of piglets during resection by grinding. As the area under investigation is small it is also important to test whether the thermographic techniques applied are able to provide data usable in this application. The procedure was performed by an experienced operator using an electric grind stone on twelve piglets 16 hours after birth. Infrared thermographic video was taken at 30 frames per second with thermal imaging camera model TVS500; different distances and camera angles from the mouth of piglets were checked. It was demonstrated that if resection of teeth by grinding is correctly performed the temperature rise is confined to the teeth themselves and does not extend to any other part of the mouth. The average baseline temperature of the mouths is 37°C. The teeth grinding procedure took on average 50 seconds per piglet to accomplish. The time grinders were applied to each tooth was less than 2 seconds. Immediately on application of the grinder the average tooth temperature reached was 50°C remaining virtually constant during the 2 seconds. The peak temperature of a tooth reached was 88°C for a sub-second interval. Teeth took 2 seconds on average to cool back to baseline temperature. It is actually possible to record a thermographic video during the grinding of the teeth of piglets without interfering with the procedure and collect valuable useable data. However, it is imperative to use a camera with spatial resolution at least equal to that of the TVS500, to ensure the accuracy of the temperature values obtained on small objects such as teeth. The distance of 0.4m between camera and subject has proved to be the optimal one and the frequency of 30 frame per second appropriate. It would seem that, with proper handling, grinding of teeth does not cause heating to the softer tissues of the mouth and only effects the tooth for a very short period of time. Further behavioural and physiological examinations would need to be carried out in a larger study to assess the overall effect of grinding on the welfare of the piglet and to further investigate the debate on the most suitable procedure for tooth resection of piglets. This is a very new and unique measure which supplies great detail and could be pivotal in understanding the true effects of such procedures on piglets.